Heated and cooled roll



Nov. 9, 1965 w. H. NORTON HEATED AND COOLED ROLL 3 Sheets-Sheet 1 Filed March 16, 1961 Nov. 9, 1965 w. H. NORTON 3,216,489

HEATED AND COOLED ROLL Filed March 16, 196i 3 Sheets-Sheet 2 3% v I ZTORNEYS Nov. 9, 1965 w. H. NORTON HEATED AND cooLED ROLL 5 Sheets-Sheet 3 Filed March 16. 1961 aw' Y 7 A TTORNE Ys UHR] United States Patent() 3,216,489 HEATED AND COOLED RGLL William H. Norton, Mundelein, Iii., assigner to Thermel Incorporated, Franklin Park, Ill., a corporation of Delaware Filed Mar. 16, 1961, Ser. No. 96,313 Claims. (Cl. 165-14) The present invention relates to improvements in heat transfer rolls and particularly to a roll which is internally heated during normal operation and is rapidly and automatically cooled at the termination of an operating run.

The present invention contemplates the provision of an electrically heated heat transfer roll having a cylindrical outer shell and a concentric cylindrical inner shell forming a chamber therebetween containing a heat transfer liuid and preferably a eutectic composition. The roll is rotatably mounted on a hollow shaft with electrical heating elements supported on the shaft. The hollow supporting shaft is stationary and provides a container for electrical leads and a conduit for air. An exhaust valve is positioned at one end of the shaft and low pressure and high pressure inlet valves at the other end of the shaft. The valves are preferably electrically operated so that they can be switch controlled for operation of the unit such as by a centrifugal switch. At the time of start up the exhaust valve is closed and the interior of the roll is pressurized with a low pressure air and the heating elements are actuated. At the end of an operating run the exhaust valve is opened and high pressure air is blown through the drum through openings in the shaft for rapidly cooling the drum interior. Other operating arrangements are possible as will be described and the rapid cooling may be effected by cooling coils embedded in the eutectic material.

An object of the invention is to provide an improved rotary heat transfer roll with improved effectiveness and efficiency well suited for a Variety of manufacturing operations wherein a cylindrical heat transfer roll surface moves in engagement with a material to be heated.

Another object of the invention is to provide an improved heat transfer roll construction having an increased margin of safety and well adapted for uses in the presence of materials which are of an inflammable or an explosive nature.

A still further object of the invention is to provide an improved heat transfer roll which can be very rapidly cooled when it is stopped so that the temperature of the roll can be maintained above the temperature of materials subject to thermal degradation for high speed operation and the roll immediately cooled when stopped to prevent damage to the material and the possibility of coniiagration or explosion.

A still further object of the invention is to provide an improved heat transfer roll wherein uniform heating of the outer surface of the roll is obtained through the use of a eutectic composition.

Other objects and advantages will become more apparent with the teaching of the principles of the invention in connectio with the disclosure of the preferred embodiments thereof in the specication, claims and drawings, in which:

FIGURE 1 is a vertical sectional view taken through the axial center of a heat transfer roll embodying the principles of the invention;

FIGURE 2 is a diagrammatic illustration of a control circuit for the roll;

FIGURE 3 is a sectional View taken through the axis of a roll embodying a modified arrangement for rapidly ,cooling the roll; v

FIGURE 4 is a vertical sectional view of a heat trans- Lce fer roll with the inner shell shown in full to illustrate construction for obtaining a uniform temperature along the roll;

FIGURE 5 is a vertical sectional view shown in somewhat schematic form of a roll standing on end illustrating steps in the method of lling the roll; and

FIGURE 6 is an enlarged detail sectional view of a portion of heat transfer roll illustrating a construction for the outer shell.

As shown on the drawings:

As illustrated in FIGURE 1, a heat transfer roll 5 includes a plurality of shells, illustrated as including an outer shell 6 with a cylindrical outwardly facing surface for engaging a surface to be heated. The roll includes an inner shell 7 which is illustrated as cylindrical and concentric with the outer shell 6 and at the ends of the shells are annular end walls 8 and 9 which with the shells deline a heat distributor chamber 10. The chamber 10 is provided with a heat distribution material which is preferably eutectic composition 10a. The eutectic composition will be solid at normal room temperatures and will become liquid at normal heating temperatures. A preferred eutectic composition will melt at 275 F. and will `be usable to 1000o F. Other eutectic compositions are suitable and for certain conditions are usable from 450 F. to 2000 F.

The eutectic material will solidify at room temperatures and therefore the problem of leakage when the machine is at rest is not present. Other heat transfer fluids which tend to damage the materials with which they come in contact are not used and the problems of providing positive seals and inspection before usage are therefore avoided. Further, the eutectic composition is much easier to handle and store and the price per pound is very appreciably less than other heat transfer fluids. The eutectic composition has a lower specific heat factor than other organic substances, which is an advantage. The eutectic composition has no boiling point and a wider practical safe range of operation. It has a good conductivity factor, higher than liquid metal. For example, sodium has the highest conductivity factor of metals and of course would be unsafe for use. Sodium has a conductivity factor of 47 while a eutectic composition suitable for use has a conductivity factor of 58. A eutectic composition which has been used and found suitable and which is within the class of preferred eutectics is commercially available under the trade name Quick Temper 275. The eutectic is inert, easy to handle :and can be safely stored over a period of time. Another advantage is its viscous properties, for example in the suitable heating range of 500 to 700 F. The viscosity is higher than liquid metal, and the eutectic composition will adhere to the surfaces of the shells for improved heat transfer in the event air spaces are left.

The eutectic composition may be placed in the chamber 10 when the shells are `assembled or may be placed therein in the iuid state through a lling 'opening provided for that purpose. The chamber shown with a pressure relief valve lifting 12 for the relief of internal pressures which may develop and the relief valve may be removable so that its connection can be used as a filling openmg.

The eutectic material in the chamber 10 lis preferably arranged so as not to completely till the entire void and to therefore leave an air space for expansion. In some circumstances it may be acceptable to use a liquid in the chamber 10 instead of a eutectic composition. A liquid such as oil is suitable but must have a flash point above Vthe operating temperature. The air space for expansion is shown at 10b and may be only large enough to permit normal heat expansion of the heat transfer material 10a in the chamber 10, inasmuch as the Valve 12 will relieve undue expansion due to overheating lor the like.

Within the rotor S adjacent the inner shell 7 is a heating means preferably in the form of a plurality of tubular electric heating elements 11. The heating elements are stationary and the rotor is mounted for rotation about its axis on end support bearings 13 and 14. The heating elements are preferably of the tubular type with wire resistance 'elements embedded in compacted electrical insulating material within the tubes, and extend axially Within the rotor. As the rotor is moved in rotation about the heating elements, heat energy is transmitted to the eutectic composition within the chamber to cause it to become liquid, and the liquid composition will evenly distribute the heat energy to the 'outer shell 6.

The rotor and the heating elements are supported on a shaft 17 shown as being hollow to contain electrical conductors 18 which are connected to the heating elements 11. The elements are stationarily supported at their ends by radial support members and 16 which may be in the form of spiders secured to the shaft. The support bearings 13 and 14 lare also mounted on the shaft.

For controllably regulating the heat of the rotor the electric current to the heating element-s 11 is controlled by a temperature responsive switch control member 19. This may be of the switchltyrpe or of the resistance thermometer type and the arrangement is shown schematically for purposes of illustration in FIGURE 2.

The control 19 is electrically coupled to the circuit through slip ring and brush elements with the slip rings shown at 20 connected to leads from the control 19 and with the brushes as shown at 21 connected to the control circuit. Within the rotor 5 adjacent the inner shell 7 is a heating means preferably in the form of a plurality of tubular electric heating elements 11. The control circuit is shown yin FIGURE 1 for purposes of illustration only as including a control relay 19a which is omitted in FIGURE 2. Electricity is supplied from the supply line 22. When the eutectic composition in the chamber reaches the desired temperature, the switch of the control 19 will open the circuit to the electrical heaters 11, and as will be appreciated, various control circuits may be employed. A centrifugal switch 39 is employed to control heating and cooling 'of the drum as a function of its rotation as will be described.

The slip rings 20 and the brushes 21 are shown as preferably located within the roll 5 so as to be surrounded by an atmosphere of non-explosive air, as will later be described.

The roll may be rotated by the friction of engagement with a surface to be heated or may be driven in rotation at a suitable speed. As illustrated, a pulley 23 may be attached to the end driven by a suitable belt 24 which in turn is driven by a motor 25 operated by a motor control 26 which determines the operation and speed of oper-ation of the motor.

As illustrated in FIGURE 1, the roll 5 is provided with means for pressurizing the interior during operation to prevent the accumulation or entry of any combustible gases, such as might be given off by material being heated. An air supply line 27 connects to the hollow shaft 17 and is supplied With a source of low pressure air for pressurizing the roll and is also .provided with a source of high pressure air for cooling the roll rapidly at the termination of an operating run. The low pressure source of air is controlled by an electrically operated valve 28 connected to a low pressure source 32 with a regulator valve 30 in the line. The high pressure air is controlled by an electrical valve 29 connected to a high pressure source 33 and a regulator Valve 31 is connected in the line. The low pressure source 32 provides a high volume supply of air to establish a positive internal air pressure in the roll. For example, a positive pressure of 3 pounds per square inch or more of pure fresh air eliminates the possibility of accumulating an explosive atmosphere within the roll. Wiring and connections are within the hollow shaft or within the roll and explosionproof operation is therefore accomplished. The discharge of the hollow shaft 17 is provided with a discharge line 34 which is controlled by an electrically operated valve 35. The valve 35 is closed during normal operation to permit pressurizing the roll.

The source 33 is a high pressure high volume source and supplies cooling air which ows through holes 36 into the roll. The air leaves through holes 3'7 also cornmunicating between the interior of the shaft and the roll and a partition 33 may be provided in the hollow shaft to insure that the air will pass through the drum before it leaves through the discharge valve 35. This supply of air is also used before beginning operation to flush out the internal roll area and insure that the roll will be filled with fresh air. As will be understo-od, the cooling effects at the end of a run are completely compatible with the low pressure explosion-proof operation. The air supply line 27 in the discharge contr-ol valve 35 serves dual purposes in controlling ushing of the roll before operation, pressurizing the roll during operation, and cooling the roll at the end of an operation `or when stopping. Flushing the interior with air immediately cools the heating elements 11 and accomplishes a radical temperature reduction on the face of the roll at an accelerated rate in the order of 5 to 1 or as much as 10 to 1 as related to cooling time under static conditions, the cooling being proportional to the total air llow rates provided.

The valves 28, 29 and 35 are preferably electrically actuated such as by a centrifugal switch 39. As illustrated in FIGURE 2, the electrical power for the mechanism is derived from a main switch 40 connected to the centrifugal control switch 39 which is mounted on an end Wall within the roll. The centrifugal switch is provided with multiple contacts so as to operate the heating elements 11 and each of the valves.

As a typical operation, as the main switch 40 is closed, the centrifugal switch 39 will open the exhaust valve 35 and the high pressure supply valve 29 so as to flush the interior of the roll 5 and exhaust any accumulated vapors. As soon as the roll starts moving, the centrifugal switch closes the valve 35, closes the Valve 29, energizes the heaters 11, and opens the low pressure valve 28 to pressurize the interior of the roll. If desired, the centrifugal switch may first purge the interior of the roll just as the roll starts rotating and the heaters may be actuated as the roll reaches operating speed.

At the end of an operating run, as the roll is stopped or slowed down the heaters 11 are de-energized and the valve 35 is opened while the high pressure valve 29 is also opened to discharge high pressure air into the interior of the roll to effect rapid cooling.

Many materials are processed on heating rolls which are subject to thermal degradation. Inasmuch as material temperature is in relation to source temperature and dwell time, for practical operation rolls are operated at a much higher temperature than is required in the processed material. This permits higher take-off speeds and increased output. Wheneveriit is necessary to stop the roll it is necessary that its surface temperature be immediately reduced below either the melt point or a point of thermal degradation of the material as quickly as possible. F-or instance, many rolls operating at 300 F. surface temperature must be dropped to 200 F. quickly before shutdown to avoid serious damage to whatever material is being run. For example in running material webs, damage done during cool down forces the rejection of lengths of material. The longer period of cool down experienced, the larger the cost of rejected materials. Of course, Within limits, the take-off speed can be reduced as the temperature falls so as to maintain a constant input value to the web during stopping. This could be controlled by slowing down the motor by the motor control 26. The present invention however contemplates cooling at an extremely rapid rate so that a correlation between speed and temperature does not have to be maintained over any substantial shutdown.

In some instances, the centrifugal switch 39 can be replaced by or combined with time delay relays so that the programming is primarily keyed to time rather than rotational speed for shutdown. Various ratios of time temperature and rotation are possible and are determined by the factors of the material being run, actual speeds used and rate of cooling of the roll. A timed operation is possible with the use of a clock although a centrifuga-l switch operating through relay controls effects a saving in the price of equipment used.

In the arrangement of FIGURE 3, a roll 5 has a construction similar to that of FIGURE l but is cooled by liquid tiowing through heat exchange -coils 41 embedded in the heat transfer eutectic between the outer shell 6 and the inner shell 7. Liquid such as cold water is conveniently used and a very rapid cooling is effected With the heat being removed from the surface of the outer shell 6 at a very rapid rate to effect almost instantaneous cooling. With this type of cooling the heating elements 11' need not be cooled, although the electrical energy is Vturned off, and a c-ooling of the roll will be effected.

Cold water coolant is supplied to the lcoils 4l through an inlet line 42 which rotates with the roll 5 and is connected to a rotatable liquid conducting connector 4S. The connector 45 may be in the form of a rotatable outer jacket with a chamber 48 therein filled with water. Water is supplied to the chamber from a supply line 44. The water is discharged at the other end of the drum through a line 43 connected to a rotating connector 46 leading to a water discharge line 47. The water will usually be drained from the coils 41 for normal operation.

Cooling with the arrangement of FIGURE 3 can be rapidly accomplished with-out a flow of air and while maintaining the interior of the roll pressurized. Air pressurization is accomplished by an inlet line 49 controlled by a Valve 50 leading to the roll interior. An outlet valve 51 may be provided but is kept closed during operation. Valves 50 and 51, and a valve 52 controlling the cooling liquid, may be controlled manually or by timer operated switches, or by a centrifugal switch 39.

As a brief summary of operation, with reference to FIGURE 1, at startup the electrical heating elements 11 are energized and high pressure air is flushed through the interior of the roll 5 by opening the valve 29 and the exhaust valve 35. The exhaust valve 35 is then closed, and the high pressure valve 29 is closed and a low pressure valve 28 is opened to maintain the interior of the drum under pressure with clean fresh air. Heat is transmitted uniformly to the outer surface of the roll 5 through the eutectic material 10.` At shutdown a rapid iiow of cooling air is again admitted to the interior of the roll 5 by opening the valve 29 and by opening the exhaust valve 35 so that the material in engagement with the roll will not be damaged When the roll is stopped.

Thus it will be seen that I have provided an improved heat transfer roll which meets the objectives and advantages above set forth. Theroll is compact and reliable in operation andemployssimpliiied connections and controls which are reliable and which are explosion proof.

While various eutectic compositions will be satisfactory in accordance with the foregoing disclosure, a preferred eutectic is a mixture of sodium and potassium nitrites and nitrates mixed to obtain a low melt point. This mixture will obtain a melt point of 275 F. or less and an operating range of 275 F. to 1000 F. has been used. The resultant eutectic also obtains a high specific heat of approximately 0.4 which is desirable in that it stores a substantial amount of energy. The thermal conductivity is also good being 5 8 B.t.u. per hour per foot per degree Fahrenheit. This conductivity is highly advantageous over organic materials, for example', and certain organics have a conductivity as low as 1/100 of this value. The cost of this eutectic mixture at current prices is about 13 a pound whereas other materials run substantially higher in cost. The boiling point of this eutectic mixture runs up to 1440 F. providing a good operating range. Boiling points on organics, and even fire resistant fluids are much lower. The material has been used with various metals for the roll including aluminum, brass, copper, rubber and plastics, with silver solders and zinc plates and no corrosion has occurred. The eutectic mixture does not have a flash point which is objectionable in organic materials. In summary, this compound has been found to be advantageous from substantially all standpoints for the purposes described.

FIGURE 4 illustrates a form of roll constructed for obtaining uniformity of temperature axially along the roll. The natural tendency of a heat transfer roll is toward a hot center and cold end. To overcome this a series of fins are installed in the chamber to create a circulation of heated eutectic from the center hot spot toward the ends which will obtain uniform temperature along the roll.

A roll 55 is shown in FIGURE 4 supported for rotation on a shaft 55 and provided with a cylindrical outer shell 57 surrounding and spaced radially from a coaxial inner shell 58 in order to provide a chamber 54 therebetween. The chamber contains a heat transfer liquid such as a eutectic of the type described above.

Mounted on the inner shell 58 are a series of outwardly projecting vanes 59 and 60 which provide surfaces that face outwardly in an axial direction so as to circulate eutectic axially. The helical vanes 59 and 60 are arranged so that they extend in a direction from the center to the end being wound in a direction opposite the direction of rotation of the drum which is indicated by the arrow 58a. Short spaces 61 and 62 are present between the ends of the vanes and the end walls 57a of the chamber 54. The inner ends of the vanes are spaced apart in an axial direction as shown by the ends 63, 64 and 65 for the vanes 59. The vanes extend successively further toward the center of the chamber 54 so that each vane will catch a separate circumferential area yof heat transfer liquid and in effect pump it outwardly. The vanes do not extend fully to the outer wall 57. The liquid will be pumped outwardly from the center and will be returned by circulating flow to the center for reheating. It will of course be understood that in some circumstances it may be desired to secure the vanes to the inner surface of the outer cylindrical shell 57.

FIGURE 5 is provided to illustrate a preferred method of filling the heat transfer roll of the invention. A roll 67 is shown with inner and outer shells to provide a chamber 68 for heat transfer fluid. A eutectic is filled into the chamber 68 preferably a mixture of sodium and potassium nitrites and nitrates. Two openings 69 and 70 are provided in the end of the chamber, one for filling and theother for permitting the escape of air.

The eutectic is provided from a heated container 71 which heats the material to 400 F. This liquid material is filled into the opening 69 as indicated by the filling line 72. l The chamber 68' is filled to a percentage of its full volume with the percentage being critical. I have found that the chamber can be filled to a volume ranging from 60 to 90% of the total volume and is preferably filled to substantially of its volume. As illustrated in FIG- URE 5, the chamber is filled to the level represented by V1 which is in the range of 60 to 90%, and is preferably 80% of the total volume which is represented by V14- V2. The remaining air space V2 of course will be in the range of l0 to 40% of the total Volume and will preferably be 20% of the total volume. l

The eutectic `is then permitted to cool and shrink and when cooled to substantially room temperature the openings 69 and 70 are closed so as to seal the chamber 68.

At operating temperatures which are substantially above 400 F. the air in the space V2 will compress but will not reach dangerous levels which would rupture the charnber 68.

For example in a chamber filled to 80% of total volume with the above eutectic at 400 F., and sealed, operation Was conducted at an operating temperature of 670 F. at an internal air pressure of 26 pounds per square inch. The original iilling at 400 F. was convenient and eliminated the moisture from the chamber in the roll and from the eutectic.

FIGURE 6 illustrates a preferred construction for certain environments providing a rolling surface having good heat transfer properties, having a long wearing life, and being free from corrosive action from the materials engaged from the air. A roll 73 has end walls 74 for supporting an inner shell 76 with a cylindrical concentric outer shell 75. The shells are separated by an annular end wall 80 to form a chamber 77 therebetween for heat transfer fluid. The outer shell is formed of layers and an inner layer 78 is preferably of metal and the outer layer 79 is of hard chrome.

Thus I have provided an improved apparatus and improvedmethod which meet the objectives and advantages above set forth. The construction presents an improved and reliable heat transfer roll adapted for numerous heat transfer operations wherein a surface must engage a heat receiving7 surface without sliding friction and transfer heat energy thereto.

It will be understood that the rolls 4, and 6 are each provided with suitable heating means such as by electrical elements non-rotatably positioned in the rolls, similar to the structures of the other ligures of the drawings. The rolls of FIGURES 5 and 6 are also provided with suitable supports for rotatably supporting the rolls and this may be done in any satisfactory manner as will be appreciated by those skilled in the art.

The drawings and specification present a detailed disclosure of the preferred embodiments of the invention, and it is to be understood that the invention is not limited to the specific forms disclosed, but covers all modifications, changes and alternative constructions and methods falling Within the scope of the principles taught by the invention.

I claim as my invention:

1. A heat applying mechanism comprising in combination a hollow roll having an outer heating surface, an air inlet line means communicating with the interior of the roll, an air outlet line communicating with the interior of the roll, a controlled low pressure source of air connected to said inlet line controlled by a rst valve for pressurizing the roll interior, a controlled high pressure source of air connected to the inlet line controlled by a second valve for rapidly cooling the roll at the end of an operating run with the air escaping through said outlet line, a third valve in said outlet line to be opened during cooling and closed for pressurizing the roll, and a common control means connected to said second and third valves for simultaneously opening these valves to relieve the pressure in the interior of the roll and cool it with a iiow of air.

2. A heat applying mechanism comprising in combination a hollow roll having an outer heating surface, an air inlet line means communicating with the interior of the roll, an air outlet line communicating with the interior of the roll, means for heating the surface of the roll, a control for said heating means, a controlled low pressure source of air connected to said inlet line controlled by a irst valve for pressurizing the roll interior, a controlled high pressure source of air connected to the inlet line 7 controlled by a second valve for rapidly cooling the roll at the end of an operating run with the air escaping through said outlet line, a third valve in said outlet line to be opened during cooling and closed for pressurizing the roll, a common control means connected to said control for said heating means and connected to said second and third valves for simultaneously opening the valves to relieve the pressure in the interior of the roll and cool it with a flow of air and to terminate operation of the heating means at the end of an operating run.

3. A heat applying mechanism in accordance with claim 1 wherein said common control means comprises a centrifugal switch mounted on the roll and being operative with rotation of the roll so that a cooling ow of air occurs automatically as the roll is stopped.

4. A heat applying mechanism in accordance with claim 2 wherein said common control means is a centrifugal switch mounted on the roll so that a iow of air through the roll occurs before a start-up and is terminated as the roll reaches operating speed with the heating means automatically operated at operating speed and so that operation of the heating means is terminated and said second and third valves are operated at the end of an operating run when the roll stops.

5. A heat applying mechanism comprising a rotatable drum having an inner surface and having an outer surface for engagement with an area to be heated, said surfaces defining an annular chamber, means for rotatably supporting said drum, a eutectic composition within said chamber solidifying at room temperatures and being liquid at operating temperatures, means for heating said eutectic composition to uniformly distribute heat energy to said outer surface during rotational operation of the drum, a conduit embedded within said composition and distributed substantially throughout the axial length and circumference of said chamber for conducting a coolant through the eutectic at the end of an operating run for rapidly cooling the surface, a coolant supply line at one end of the drum, a rotary connection connecting the line to one end of the conduit, a coolant discharge line, a rotary connection connecting said discharge line to the other end of the conduit, and valve means in the coolant supply line for stopping the coolant supply so that the conduit can be drained of coolant for rotational operation when the composition is heated.

References Cited by the Examiner UNITED STATES PATENTS 1,278,155 9/18 Jefferson 16S-90 X 1,754,286 4/30 Hitchcock 192-4 1,820,074 8/31 Kilborn 165-89 X 2,431,473 11/47 Flynn 16S-14 2,483,021 9/49 Oaks 16S-107 X 2,599,346 6/52 Offen 16S-89 2,777,480 1/57 Linda 53-25 '2,779,143 1/57 Brooks 141-11 2,797,899 7/57 Funk et al. 165-89 X 2,902,774 9/59 Swaney 165-89 2,912,556 11/59 Hold 165-64 X 2,933,885 4/60 Benedek et al. 16S-18 3,020,383 2/ 62 Onishi et al 219-37 3,074,695 1/63 Hold et al 16S-90 X 3,080,150 3/63 Gross 165-89 X 3,094,065 6/63 Roberts 101-148 3,105,133 9/63 Norton 16S-104 X FOREIGN PATENTS 5,833 7/03 Denmark. 839,446 5/52 Germany.

o CHARLES SUKALO, Primary Examiner.

HERBERT L. MARTIN, ROBERT A. OLEARY,

' Examiners. 

1. A HEAT APPLYING MECHANISM COMPRISING IN COMBINATION A HOLLOW ROLL HAVING AN OUTER HEATING SURFACE, AN AIR INLET LINE MEANS COMMUNICATING WITH THE INTERIOR OF THE ROLL, AN AIR OUTLET LINE COMMUNICATING WITH THE INTERIOR OF THE ROLL, A CONTROLLED LOW PRESSURE SOURCE OF AIR CONNECTED TO SAID INLET LINE CONTROLLED BY A FIRST VALVE FOR PRESSURIZING THE ROLL INTERIOR, A CONTROLLED HIGH PRESSURE SOURCE OF AIR CONNECTED TO THE INLET LINE CONTROLLED BY A SECOND VALVE FOR RAPIDLY COOLING THE ROLL AT THE END OF AN OPERATING RUN WITH THE AIR ESCAPING THROUGH SAID OUTLET LINE, A THIRD VALVE IN SAID OUTLET LINE TO BE OPENED DURING COOLING AND CLOSED FOR PRESSURIZING THE ROLL, AND A COMMON CONTROL MEANS CONNECTED TO SAID SECOND AND THIRD VALVES FOR SIMULTANEOUSLY OPENING THESE VALVES TO RELIEVE THE PRESSURE IN THE INTERIOR OF THE ROLL AND COOL IT WITH A FLOW OF AIR. 